The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a vacuum processing system necessary to remove material from and deposit material on a substrate. In general, plasma is formed within the processing system under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the system (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
Although the formation of a population of charged species (ions, etc.) and chemically reactive species is necessary for performing the function of the plasma processing system (i.e., material etch, material deposition, etc.) at the substrate surface, other chamber component surfaces on the interior of the plasma processing chamber are exposed to the physically and chemically active plasma and, in time, can erode. The erosion of exposed chamber components in the plasma processing system can lead to a gradual degradation of the plasma processing performance and ultimately to complete failure of the system.
As an example, during plasma etching for semiconductor device fabrication, the termination of the peripheral edge of the substrate is important and, when not addressed properly, can change plasma properties and affect etching uniformity. A chamber component, known as a focus ring, is located beyond the peripheral edge of the substrate and, dependent on the material composition of the focus ring, it may spread or confine plasma above the substrate to improve etching performance, such as etching uniformity, especially at the peripheral edge of the substrate. However, the focus ring is consumed during plasma etching, which in turn degrades etching uniformity. And, as a consequence, the focus ring must be replaced about every 200-400 hours the plasma processing system is in operation.
As another example, during plasma etching for semiconductor device fabrication, chamber matching is also a critical concern. The consumption of chamber components (e.g., focus ring, cover ring, electrode plate, etc.), the deposition of polymer on chamber components (e.g., deposition shield, etc.), and chamber capacity change the capacitance of plasma processing chamber, which results in variable plasma properties as well as variable etching uniformity.